Engines may use boosting devices, such as turbochargers, to increase engine power density. Thus, under steady state operation, smaller displacement, turbocharged engines can produce power equivalent to larger displacement engines. However, under dynamic driving conditions, the smaller turbocharged engine may have less transient performance than a larger, naturally aspirated engine.
As one example, when a turbocharged engine is operating at low load, the turbocharger speed is low and intake manifold pressure is low. When the engine load is suddenly increased, there may be a lag before the turbocharger speed increases and intake manifold pressure rises. This delay may be referred to as “turbo-lag.” During this delay, the engine power or torque output may be less than desired value, and less than the steady state available output.
One approach that attempted to provide intake manifold pressure boost with minimal delay is described in SAE paper 670109, published in 1967. This system used storage tanks to store compressed air with a carbureted, otherwise naturally aspirated gasoline engine. In this system, when the system was actuated, desired boost pressures were achieved rapidly.
Another approach is described in JP 59-99028. This system uses a compressed-air injecting port receiving air from a compressed-air tank, where the port was formed in a valve seat of the intake valve, and said port is opened when the intake valve is opened. An on-off valve is opened transiently for a prescribed period when an accelerator pedal is rapidly depressed. When the intake valve is open, air is injected through the valve seat for supplementing lack of air caused transiently when the accelerator pedal is depressed. Specifically, when the accelerator pedal depression signal exceeds a prescribed value, the on-off valve is opened by a computer for a prescribed period corresponding to the pedal depressing speed. With such a system, boost compensation is allegedly unnecessary.
However, the inventors herein have recognized disadvantages with each of the above approaches. For example, if using the storage approach of SAE 670109 on an otherwise naturally aspirated engine, boost was provided for only a limited time since storage tanks were the only source of compressed air. Further, the system required two tanks of about 12 inches in diameter each, thus requiring significant packaging space in the vehicle.
Likewise, regarding the approach in the abstract of JP 59-99028, significant air-fuel ratio control errors may be encountered if such a system were applied to a gasoline engine. Specifically, the additional air provided by the boost system may not be measured by a manifold pressure sensor or mass airflow sensor in the intake manifold, and thus the amount of fuel supplied may not match the total inducted airflow, resulting in an air-fuel ratio excursion. Furthermore, it does not appear that the energy of compression of the added air is used to amplify air flow through the main intake port. This means that the compressed air tank must be large enough to supply all of the desired increase of intake air mass.
Thus, in one approach, the above disadvantages may be overcome by a system for a vehicle traveling on the road. The system comprises: an engine having at least a cylinder; a fuel injector coupled to said cylinder; a compression device coupled to said engine; a compressed air storage device coupled to said compression device and configured to deliver compressed air to said cylinder through an air amplifier device; and a controller to adjust an amount of fuel injection to account for variation of compressed air delivered to said cylinder from said compressed air storage device.
In this way, it is possible to provide accurate fueling amounts, even when unexpected changes in an amount of compressed air are encountered before or during an intake event. Further, the ability to provide rapid response to variations in delivered compressed air enables further exploitation of the ability to accommodate the earliest possible induction of such compressed air, thereby further increasing engine transient responsiveness.
Note that various types of fuel injectors may be used, such as side direct injection, overhead direct injection, and port injection.